1. Field of the Invention
This invention pertains to conversion of natural gas to acetylene. More particularly, natural gas is converted to reactive hydrocarbons comprising acetylene with externally derived hydrogen sources and the reactive hydrocarbons are reacted to form hydrocarbon liquids.
2. Description of Related Art
Conversion of natural gas into hydrocarbon liquids has been a technological goal for many years. The goal has become even more important in recent years as more natural gas has been found in remote locations, where gas pipelines may not be economically justified. A significant portion of the world reserves of natural gas occurs in such remote regions. While liquefied natural gas (LNG) and methanol projects have long attracted attention by making possible conversion of natural gas to a liquid, in recent years the advent of large scale projects based upon Fisher-Tropsch (F-T) technology have attracted more attention.
The conversion of natural gas to unsaturated hydrocarbons and hydrogen by subjecting the hydrocarbons in natural gas to high temperatures produced by electromagnetic radiation or electrical discharges has been extensively studied. U.S. Pat. No. 5,277,773 discloses a conversion process that subjects methane plus hydrocarbons to microwave radiation so as to produce an electric discharge in an electromagnetic field. U.S. Pat. No. 5,131,993 discloses a method for cracking a hydrocarbon material in the presence of a microwave discharge plasma and a carrier gas, such as oxygen, hydrogen and nitrogen, and, generally, a catalyst. U.S. Pat. No. 3,389,189 is an example of patents relating to production of acetylene by an electric arc.
Methane pyrolysis to acetylene by rapid heating in a reaction zone and subsequent rapid quenching has also been extensively investigated. Subatmospheric pressures and specific ranges of velocities of hydrocarbon gases through the reaction zone are disclosed in U.S. Pat. No. 3,156,733. Heat is supplied by burning of hydrocarbons.
In particular, we refer to U.S. Pat. Nos. 6,130,260; 6,323,247 and 6,602,920 by Hall et al. Hall et al. do not claim or disclose separation and isolation of the acetylene from the other gas components prior to hydrogenation. We provide a process step whereby the acetylene is selectively separated from the other gas components prior to hydrogenation, and directed as a discrete product stream. This reduces the amount of gas, such as ethylene, that must be treated in the hydrogenation step. The ethylene may be removed from this hydrogenation stream and combined with the product stream of the hydrogenator thus increasing overall yield of acetylene in a discrete product stream. Hall et al. do not separate ethylene from any stream for recycling to form acetylene.
Although the prior art has disclosed a range of methods for forming acetylene from natural gas, an energy-efficient process for converting natural gas to an isolated acetylene product has not been available.